Chaser for die heads



Ema/Mom March 28, 1939. c. A. REIMSCHISSEL CHASER FOR DIE HEADS FiledJuly 3, 1937 Patented Mar. 28, 1939 2,152,567 cmsaa Fox ms nmns CharlesA. Reimschissel, Waynesboro', Pa" assignor to Landis Machine Company,Waynesboro, Pa., a. corporation of Pennsylvania Application July 3,1937,Serial No. 151,913

5 Claims.

This invention relates to thread cutting chasers and holders andparticularly to chasers of the tangential type.

Chasers of this kind are, as is well known in the art, held in suitableholder blocks by means of clamps drawn into firm engagement withclamping surfaces provided on the chasers. An example of this kind ofchaser mounting is had in United States Patent No. 1,906,176, granted toS. F. Newman et al. on April 25, 1933. As will be readily understood, aconsiderable force must be exerted on the chaser by the clamps to theend that the chaser is held firmly against the co-operating seatingsurface on the chaser holder to prevent relative movement between thesetwo elements. Also, in order to insure accuracy and uniformity ofperformance of the respect to the seating surfaces, which not only,results in inaccuracies in the cutting action, but,

furthermore, tends to greatly reduce the force of friction betweenchaser and holder thereby making it possible for the chaser to moveslightly with respect to the holder under the reaction forces set upduring the cutting operation.

It is, therefore, a major object of this invention to provide animproved thread chaser and holding means so designed that the resultantof the force exerted by the holding or clamping means is directedcentrally of the seating surfaces and perpendicular thereto, whereby thetendency of the clamping force to tilt the chaser is obviated. 7

Another important object of my invention is to provide a chaser orthread cutting tool with clamping and base seating surfaces so arrangedwith respect to each other and to a back seat ing surface that theclamping force is reflected by the first two surfaces as a resultantacting centrally of and perpendicular to the back seating surface of thechaser and also centrally of and normal to the seating surface of theholder.

A still further object of my invention is to provide a novel andimproved chaser holder and clamp in which the clamp seating surface ofthe holder and the clamping surface of the clamp are each inclinedequally from a line parallel to the clamp securing means whereby theforce applied to the chaser is directed parallel to the back seatingsurface of the chaser and thus intersects the clamping surface of thechaser and In devices of this character, the force applied by theclamping means is of considerable magnitude, as has been previouslynoted, and, furthermore, the chasers are made of high speed steel whichsometimes leads to failure of the chaser by cracks starting at the acuteangle of the dovetail usually provided adjacent to the chaser clampingsurface. It is, therefore, a still further object of my invention toprovide an improved thread chaser which is formed so as to eliminatethis sharp angle between the clamping surface and the body of the chaserthereby preventing the formation of incipient cracks and greatlyenhancing the strength and life of the chaser.

Also, in chasers of this type, wherein the clamp seats against aninclined clamping surface, another place of weakness is present at thejuncture of the clamping surface and the back seating surface of thechaser. Due to the relative brittleness of the material used for thechasers and the intensity of the clamping force, the thin and sharpedges formed by the aforementioned surfaces is very often chipped orbroken under the clamping action. Thus, a still further object of myinvention is to provide an improved chaser in which a comparativelythick edge is located at the juncture of the clamping surface and backseating surface, which thickened edge is sufficiently strong towithstand the clamping forces.

The above, and further objects, will become apparent from a study of thefollowing detailed description of a preferred embodiment of my inventiontogether with the appended claims when considered in conjunction withthe accompanying drawing, in which:

Figure 1 is a face view of a die head provided with a set of chasers intheir holders and embodying my invention.

Figure 2 is a partial section through a chaser and its holder taken onthe line 2-2 of Figure 1, and on an enlarged scale.

Figure 3 is a view similar to that of Figure 2, taken on the line 3-3 ofFigure 1.

Figure 4 is a face view of the improved chaser of my invention; and

Figure is an end view of a slightly modified form of chaser.

Referring now to the drawing, in which like reference characters areused to designate the same elements wherever they appear in the severalviews, and with particularreference to Figure 1, the reference character2 designates a conventional die head carrying holders 4. Chasers 6 aremounted in the holders by means of clamps 8 held in place by screws ll.

' Turning now to Figure 2 and 8 wherein the shape of my improvedchasers, holders, and clamps are shown, chaser 8 is provided with baseseating surface i2, back seating surface It, and clamping surface l4.Small beveled surfaces It and 20 connect these three surfaces as will beevident upon inspection of these views. The surface I4 formsa dovetailand is connected by undercut surface 22 to a seating surface 24, thelatter being parallel to, but offset from, surface it. Surfaces I-4 and22 are formed by a curved surface or fillet 20, the purpose of whichwill be explained later. Chaser t is provided with cutting serrations 20and a leading edge 30 in the usual manner.

Surface It bears against aco-operating flat surface 32 on holder 4, andbase surface i2 bears against a co-operating surface 34. Surface 24rests against a surface ll to give support to the leading edge of thechaser. The holder is also provided with a surface ll on which rests anend surface 40 of clamp l. The opposite end of the clamp carries aninclined surface 42 engaging surface i4 of chaser 8.

The angular relationship of the several surfaces is illustrated by thebroken lines R, :c, y, and 'z and angles H in Figure 3. Surfaces 30 and34, and co-operating surfaces 40 and I2 are parallel (see lines 1 and u)Surfaces l2 and I4 are each inclined equally with respect to surface it(see lines 1! and z and angles ma). Since the axis of screw it isparallel to surface :2, it follows, by simple geometry, that surfacesI4, 42 and 38, 40 are equally inclined with respect to the line ofaction of the force exerted in holder 8 by the screw IO.

Upon tightening of screw II, the clamp is pressed at one end againstsurface a while the other end bears on the inclined surface l4 of thechaser; and, as will readily be understood, the chaser is firmly held inplace'in the holder by screw it with surfaces It and 32 and surfaces 24and 36 pressed together, and with surfaces i2 and 34 also engaged.

It will be observed that, due to the equal in,- clinatlon of surfacesll, 40 and I4, 42 with respect to the direction of the force exerted bythe screw it, the resultant force acting on chaser surface l4 will bedirected in parallelism with the surfaces It and 82. Furthermore, assurfaces l2 and H are equally inclined with respect to the surface It,the resulting clamping force reacts equally against each side of thechaser 6, on the surfaces I4 and I2, and the back seating surface it isforced against the surface 32 of holder ill with a uniform pressurethroughout. In other words, the resultant of the clamping force actsnormal to and centrally of surfaces It and 32 (see line It, Figure 8).

As a consequence of this arrangement of the several mutually engagingsurfaces, there is no tendency for the clamping force to tilt" or' "cockthe chaser in the holder, and a maximum frictional grip is provided. Inthis manner the chaser is held in place on the holder with the utmostsecurity, and upon adjustment therealong, as is nwessary after grinding,isalways returned to the same relative position with respect to theholder, as far as the location of the cutting serrations is concerned,thus insuring accuracy and uniformity of performance of the chaser.

It will also be observed that the chaser has a relatively thickened edgeadiacent'to the bevel It to resist the stress resulting from thepressure of clamp I. with this arrangement an unusually strongsupporting surface is provided, and danger of damaging the chaserby"chipping or "breaking" at this point is greatly reduced and, in fact,practically eliminated.

Also, the provision of the fillet 2. adds considerably to the abilityofthe chaser to stand up under the clamping strains. This is due to thefact that incipient cracks resulting from hardening strains generallypresent at this point when the surfaces l4 and 22 are joined by an acuteand sharp angle, as is the usual practice, are obviated. Thus, thetendencyof the chaser to break at this point is practically eliminated.

. The bevel 20 also serves a very useful purpose by preventing chipping"and "breaking", and

further provides a clearance space into which fine chips or cuttings maycollect, thus permitting proper seating of thesurfaces l2 and 84.Furthermore, with this construction, slight wear in the cutter used tomachine the surfaces" and 34 on the holder will not cause trouble in thelater fitting of the chasers.

The clearance surface 22, which may take the slightly modified form 22ashown in Figure 5, in which corresponding portions of the chaser aredesignated by reference characters similar to those of Figures 2 and3with the addition of the letter a makes it possible to machine the twosurfaces l4 and-24, and Ma and 24a, with a combination cutter. Thisgreatly facilitates the production of chasers and results in aconsiderable savings.

From the foregoing it will be evident that I have provided a novel andimproved chaser and chaser holding means wherein the chaser is greatlyincreased in strength and durability and is held in place in the holderin a very positive and accurate manner.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefore, to be considered in all respects asillustrative and not restrictive; the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription; and all changes which come within the meaning and range ofequivalency of the claims are, therefore, intended to be embracedtherein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A chaser holder having a surface adapted to co-operate with the backseating surface-of a chaser, a second seating surface inclined withrespect to said first named holder surface, and a clamp seating surfaceoffset from and parallel to said second seating surface, said holderbeing provided with a threaded clamping screw bore having its axisarranged parallel to said flrstnamed surface.

2. In combination a chaser, a chaser holder and a chaser clamp means,said holder being provided with offset and parallel surfaces and havinga seating surface; a chaser having a seating surface engaging saidholder seating surface and a sec- 0nd surface engaging one of saidoffset surfaces, a clamping surface on said chaser, said second surfaceand said clamping surface being equally inclined with respect to saidseating surface; said clamp means having seating surfaces engaging saidchaser clamping surface and the other of said oflset surfaces; means toapply a force to said clamp means; said clamp seating surfaces and thesurfaces on said chaser and holder co-operating therewith being inclinedequally with respect to the line of action of said force whereby theresultant of said force is directed normal to and centrally of saidholder and chaser seating surfaces.

3. A chaser comprising a body portion having a back seating surface; asecond seating surface on said body, said last named seating surfacebeing offset from and parallel to said back seating surface; a clampingsurface inclined with respect to said seating surfaces and joined at oneedge to said back seating surface by means of a beveled portion; anundercut surface joining the other edge of said clamping surface to saidoffset surface; said undercut surface extending a substantial distancebeyond said first named edge of said clamping surface, and a baseseating surface inclined toward said clamping surface, said base seatingsurface and said clamping surface making equal angles with said backseating surface.

4. A chaser comprising a body having cutting serrations thereon andprovided with a clamping surface, a base seating surface, a. first backseating surface and a second back seating surface offset from andparallel to said first back seating surface, said seating surfaces beingadapted to seat against corresponding holder surfaces, and. saidclamping surface being adapted to cooperate with a corresponding clampsurface; said clamping surface and said base seating surface beinginclined equally with respect to said back seating surfaces and towardeach other, so that the resultant of a clamping force applied to saidclamping surface in a direction parallel to said back seating surfacesacts centrally of and perpendicular to said back seating surfaces.

5. In a chaser holding device, a chaser holder, a clamp means and meansto apply a force to said clamp means, two parallel and offset chaserback seating surfaces on said holder, a chaser base seating surface anda clamp engaging surface on said holder, said last-named two surfacesbeing inclined with respect to said back seating surfaces and parallelto each other, a chaser contacting surface and a holder engaging surfaceon said clamp means, and means for applying a clamping force to saidclamp in a direction parallel to 88 said offset chaser back seatingsurfaces, said clamp surfaces being inclined equally with respect to theline of action of the force applied to said clamp.

CHARLES A. REIMSCHISSEL.

